Certain articles of manufacture such as charcoal cigarette filters, individual-sized packets of granular food products or condiments, capsuled pharmaceuticals, ammunition and the like require repetitive placement of precisely metered charges of particulate matter at some location along the production-line procession of the articles. During high speed mass production of such articles it is difficult to achieve consistent accurate filling of the desired cavities with the granular particles. In the case of filling cigarette filter cavities with charcoal, it is desirable to avoid excessive pulverization and scattering of the particulate material, while achieving as close to 100 percent fill of the cavities as possible
U.S. Pat. No. 5,875,824, which is incorporated by reference herein in its entirety, discloses a method and apparatus for delivering predetermined amounts of material, wherein a metering wheel receives discrete amounts of material from a supply chute, with the discrete amounts of material being transferred from the metering wheel to a transfer wheel, and from the transfer wheel into spaces along a filter rod. As a result of the transfer of particles from one wheel to another, the pockets for receiving the particulate material in the transfer wheel must be larger than the pockets in the metering wheel. This arrangement makes it difficult to achieve 100 percent fill of the cavities in the article receiving particulate material from the transfer wheel.
According to the '824 patent, granular particles of charcoal are drawn from a chute in communication with a reservoir into pockets on a rotating metering wheel. The rim of the metering wheel includes a plurality of equally spaced-apart pockets, each of which is defined by a radially directed, conical bore and a discrete screen at the base of the conical bore. The conical bore is convergent in the radially inward direction. A radially directed channel within the rim of the metering wheel communicates a backside of the screen with the interior of the metering wheel. A vacuum can be communicated from a stationary vacuum plenum in the interior of the metering wheel through the radial channel and screen such that any granular particles of charcoal that are adjacent the pocket in the metering wheel will be drawn into the conical bore of the pocket until it is filled.
The provision of discrete screens at the base of each conical bore creates assembly problems and increases the expense of the system taught by the '824 patent. The individual screens can also restrict airflow into the pockets to an undesirable extent.